This invention relates generally to biocompatible materials useful in the field of medical devices, and more particularly to expanded polytetrafluoroethylene (hereinafter “ePTFE”) material with a combination of improved properties, including mechanical strength and reduced thickness, and a method for producing this material.
The highly functional ePTFE material is used for numerous different purposes in the medical field. One of the most prominent uses is to encapsulate a stent made of metal between two layers of ePTFE. The ePTFE provides the metal stent with a covering, which enables the patency of the device as well as providing a more laminar flow of blood through the device. In addition, ePTFE material expands and contracts with the stent, allowing greater flexibility in introducing the device into a body and in deploying the device at a desired location.
The ePTFE material is advantageous for medical use because of its healing properties due to a porous microstructure. This microstructure consists of spaced apart nodes and fibrils, which permits the transmural migration of capillaries through its matrix. Additional advantages of ePTFE over other biocompatible materials used in the medical industry are the expandability and recovery characteristics of the ePTFE as well as its relative compliance and patency. In addition, ePTFE can be manipulated to accentuate many of its desired attributes. For instance, ePTFE can be made more porous to further promote healing characteristics, or can be made more expandable to promote compliance aspects.
The ePTFE material is advantageous for medical use because of its healing properties due to a porous microstructure. This microstructure consists of spaced apart nodes and fibrils, which permits the transmural migration of capillaries through its matrix. Additional advantages of ePTFE over other biocompatible materials used in the medical industry are the expandability and recovery characteristics of the ePTFE as well as its relative compliance and patency. In addition, ePTFE can be manipulated to accentuate many of its desired attributes. For instance, ePTFE can be made more porous to further promote healing characteristics, or can be made more expandable to promote compliance aspects.
Strength is another quality of ePTFE that can be enhanced through manipulation of the material. The strength of the ePTFE is very important because of the difficulties and invasiveness of multiple surgeries. Lack of material strength could result in its tearing or ripping, which would necessitate frequent replacing of the device. Thus it is often desired to improve the strength component of ePTFE through manipulation of the material. This is especially true for single layer ePTFE grafts that are utilized to create a skin around an implantable structural support device, such as a stent. In many cases, conventional ePTFE grafts of sufficient strength to operate effectively as a single tubular layer possess a profile or wall thickness that is far too thick for percutaneous delivery. Thus, when overall profile of the implanted device is a leading consideration, a single layer ePTFE graft must be provided with a very small wall thickness, yet be strong enough to maintain its patency under adverse conditions. Up until now, there has not been disclosed a method of producing such a material.
Consequently, there exists the need for an ePTFE material with a reduced profile that has significantly improved strength characteristics compared to similarly sized prior art material, and a method for producing the same.